Optimization of a multi-drug lateral flow immunoassay strip for use in an Abstinence Monitor is proposed. The Abstinence monitor is comprised of two main components: The collection component and the detection component. The collection component consists of a patch that continuously collects drugs excreted transdermally via sweat and other means. The collection component immediately transfers the collected material to a detection component. The detection component is the subject of the proposed Phase I research, and comprises of a lateral flow immunoassay system that will be optimized to detect very low levels of up to five drugs delivered from the collection component over periods of up to 7 days. The detection component will also be optimized to produce a permanent positive result when presented with alternating flows of drug-containing and drug-free sample, in any order, such as might be seen over the course of a single week in a user of controlled substances. Taken together, both components comprise of a device that is approximately 4cm x 6cm x lmm and is placed on the arm or other suitable site of an individual being monitored for drug use as a part of e.g., an outpatient drug treatment program. PROPOSED COMMERCIAL APPLICATION: The Abstinence monitor fills a clinical need that is not addressed by any product currently on market. Optimally, drug and alcohol treatment centers would continually monitor clients for abstinence from alcohol and durgs, but are currently unable to do so. As more health care payers require outpatient treatment as a way of reducing costs, the need for a constant, reliable method of monitoring abstinence becomes even more critical. Our two market research studies indicated a high level of interest in the Abstinence Monitor from substance abuse treatment physicians.